Detection of the Nitric Oxide Dayglow on Mars by MAVEN/IUVS

• Published in: Journal of geophysical research. Planets 2019-05, Vol.124 (5), p.1226-1237
• Main Authors: Stevens, Michael H., Siskind, David E., Evans, J. Scott, Fox, Jane L., Deighan, Justin, Jain, Sonal K., Schneider, Nicholas M.
• Format: Article
• Language: English
• Subjects: airglow; Atmospheric chemistry; Atmospheric entry; Atmospheric evolution; Dayglow; Density; Diagnostic systems; Mars; Mars atmosphere; Mars missions; Mass spectrometers; Mass spectrometry; Nitric oxide; Orbital resonances (celestial mechanics); Organic chemistry; Photochemicals; Photochemistry; Radiance; Remote observing; Resonance fluorescence; Satellite observation; Solar activity; Spectrometers; Upper atmosphere
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2019JE005945

We report the first remote observation of nitric oxide (NO) densities on Mars. The Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile Evolution (MAVEN) satellite observes NO γ band solar resonance fluorescence between 213.0 and 225.5 nm. We invert an average dayglow limb radiance profile to retrieve a number density profile between 80 and 130 km. The retrieved IUVS NO number density at 117 km is 5 times smaller than those measured by Viking mass spectrometers over 40 years ago but consistent with photochemical model results within the IUVS statistical uncertainty. These observations may therefore help to reconcile a longstanding problem in our understanding of NO photochemistry in the Martian upper atmosphere. We also report the first detection of the CO+ First Negative bands in the Martian dayglow near 219 nm. Plain Language Summary Nitric oxide has been an important diagnostic for the effects of solar activity since its detection in the Earth's upper atmosphere over 50 years ago. We report the first remote observation of nitric oxide densities on Mars. The densities are five times smaller than those measured by Viking mass spectrometers upon entry into the atmosphere over 40 years ago. These new nitric oxide observations may help to reconcile a longstanding problem in our understanding of NO chemistry in the Martian upper atmosphere. Key Points First remote observations of nitric oxide densities on Mars Nitric oxide densities are a factor of five smaller than those reported by Viking over 40 years ago Photochemical model results show much better agreement with the new remote observations than with Viking measurements